1. Field of the Invention
This invention relates to an eraser of the type that is particularly designed to remove ink from white marker boards.
2. Description of the Prior Art
A white marker board (or light shades of tan) is generally a vertically mounted writing surface, that is written upon with felt-tipped pens, and that dispense a contrasting color ink that "dries" on the board. The writing is of a non-permanent ink which when "erased" becomes a loose dust that is removed from the board with the use of an eraser.
Typically, a white board is erased with a traditional felt type eraser, which was originally designed for use on black slate boards. The use of such a traditional felt (or foam type) eraser designed for slate blackboards, presents many problems for white board use. There are several reasons for the problems. A felt eraser is intended to remove white chalk dust from the porous surface of a slate board. Excess chalk dust, not held by an eraser, drops to the chalk tray, leaving the blackboard a dark shade of gray, but sufficiently dark to contrast with newly applied white chalk. The chalk dust drops from the board to the chalk tray, or is picked up by a clean felt eraser, since no static charges are generated during this procedure.
Additionally, the felt eraser re-fills pores in the slate board with chalk dust during the erasing operation, providing the user with a "chalked-in" board at all times. (Note that a brand new blackboard must be "chalked in" to prevent permanent "ghosts" that would occur if it were immediately written upon with chalk.)
A new white board, on the other hand, has a totally non-porous finish. The white board surface is normally porcelain, melamine, (resin finish) or plastic (polyester, etc.). Erasing marker dust from a white marker board using a "standard felt eraser" can and does cause static charges to build up through triboelectric forces, particularly on melamine and plastic surfaces. As the marker dust is not as dense as chalk dust, it does not drop off white boards, but has a tendency to adhere to the board's surface. This clinging problem is especially prevalent when static charges are generated. When the felt eraser becomes "saturated" with synthetic light, marker board ink dust, it redeposits, or pushes the dry ink to other portions of the white board. This condition makes the white board irregularly blotchy with dust, and very difficult to read, as well as unattractive.
A white board, after being subjected to the chemical solvents present in most of the marker pen inks and various types of chemical cleaners used to clean the board, gradually goes from a non-porous glazed surface (when new) to a more open porous surface. This condition is similar to a porcelain sink that has been scoured too often and from which the porcelain glaze has been removed. This treatment leads to a condition known in the industry as "ghosting". Ghosting occurs as marker pen ink flows down into the porous surface and dries. When a white board surface has been ghosted, only the top dust is removed when it is conventionally erased. The dried ink trapped below the surface remains there, creating "ghosts" of previous writings.
The ideal white board eraser should address the problems of ghosting caused by worn/porous white board surfaces.
Finally the ideal white board eraser should be easy to use, easy to clean, capable of renewing its dust holding ability; and comfortable to hold. Ideally it should be sized no larger than a standard eraser (2".times.5".times.1.5" typically), as it must fit on the small trays provided on most white boards. Such an eraser ideally would be disposable after a life of 10-20 times that of a standard felt eraser, that was properly cleaned 10-20 times.
There have been many attempts to solve each of these concerns for the ideal eraser, but none of them has proven satisfactory by themselves and certainly not in concert with one another.
The Green U.S. Pat. No. 1,852,114 discloses a renewable surface dust cloth, that is composed of a plurality of thin, fibrous, loosely compacted layers.
While Green addresses the need for a "loose nap" material to increase dust holding capacity, the paper wadding structure disclosed is too weak to function as an eraser surface on a white board for any substantial time. While Green mentions impregnation of his dust cloth with an oil to increase its dust holding capacity, Green does not provide the convenience and hygienic factor of keeping the user's hand from touching a partially used surface, or one that contains an oil conditioner. Green provides no handle, no easy storage arrangement of holding, and then of discarding a layer of fabric after use, without handling the soiled layers.
The Harter U.S. Pat. No. 2,414,872, discloses a blackboard cleaner which includes a handle to which a laminated pad is mounted. The pad includes a number of plies or sheets of fabric that have been impregnated with a chemical to facilitate cleaning and prevent chalk dust.
The plies or sheets that make up the pad are vertically stitched to a tape, so that side portions of the sheets can be folded to bring surfaces of the plies to the front for use.
While Harter provides a more durable erasing surface, it would be necessary to clean the plies to obtain any reasonable economic life of the device. The Harter handle would not be satisfactory for white board use as it is cumbersome, and upon lifting, the soiled layers would likely revert to the original configuration and contact by the user would be necessary to expose a clean surface.
The Nebelung U.S. Pat. No. 1,587,670, discloses a device for polishing shoes and other articles, which includes a block carrying an endless band of fabric, the soiled surface of which must be handled to bring a fresh surface into use. The life of the Nebelung device is very limited, and requires excessive exposure of the soiled surface to the user's hands, as well as inconvenience due to the necessity of indexing or refilling the endless loop.
The Darling U.S. Pat. No. 2,648,863 discloses a blackboard eraser that is a hand held device, including a handle carrying a pad of material, but does not provide any structure to conveniently remove a soiled sheet of material without touching the soiled surface. Additionally, multiple layers (i.e., 10-20) of material could not be held by the holding tabs which Darling describes.
The Brouty U.S. Pat. No. 2,465,194, Walkama, No. 2,702,913, and Oviatt, No. 3,613,146, disclose various attempts to increase the dust holding or carrying capacity of a hand held device by providing a roll of material in the handle area. The use of a roll of material becomes unsatisfactory for white board eraser use when the bulk of such a device is considered.
The Bergquist U.S. Pat. No. 2,708,761, Walkama, No. 2,702,913 and Hensley, No. 2,693,610, disclose the use of adhesives to hold together adjacent layers of material. Adhesively held layers of material are susceptible to many shortcomings. The leading edges of the material tend to roll up due to friction, exposing the adhesive layer to the surface to be cleaned. Adhesive transferred to the board would reduce its use as a writing surface, and would also trap loose marker board dust. Renegade adhesive could also be retained on newly presented layers resulting in the described conditions.
Another commercially available white board eraser holds 25 replacement tissues, and is offered by Schwan Stabilo U.S.A., Inc. The used tissues are not easily disposed of as the user must handle the remaining stack of replacement tissues each time they are changed, which requires dismantling the eraser's components. If these tissues were to incorporate a conditioning and anti-static treatment (which they do not), handling them would be very messy and inconvenient, since to change a surface, the entire device must be "disassembled". This device lacks holding ability, as the spongy foam pad held by the handle fails to keep the fabric layer taut, so that the exposed fabric layer easily becomes loose, develops creases and folds during use. Schwan also requires that it be reloaded with replacement tissues to make it economical for use.
The eraser of my invention does not have the shortcomings of the prior art and provides many positive advantages.